I was looking for a similar answer. I crop on the site but it doesn't change the preview image, as far as I could tell, but I assumed the cropped version is the one that uploads (I don't which cards I crop to check).
On this note I wasn't sure what version the person reviewing is looking at.
When I get permission to review my own scans do they stay in my personal queue until I look at them or can others still see them before I have a chance to crop them?
It would take away some pressure to speed through my reviews.